The present invention relates to a safety device for detecting vibration such as seismic shocks and cutting off an electrical power supply when such vibrations occur.
One of the big dangers that results from earthquakes is the shorting of power lines to create fire and shock hazards before appropriate action can be taken. A device is needed to quickly and effectively interrupt the power when such an occurrence takes place.
Various typs of switching devices have been proposed in the part. U.S. Pat. No. 4,103,697 discloses such a device utilizing a pendulum with a post engaging a pad on a spring loaded finger that extends into a pocket 24 on a spring loaded arm. Movement of the pendulum causes mechanical disengagement of the post from the pad and the finger is moved upward out of the pocket or latch with the arm 20 being moved inward by another spring to close a gas valve. This device is costly and mechanical in operation. There is the possibility that the post can hang up on the pad. Also, the operation of the device depends upon the springs and their tension.
U.S. Pat. No. 4,028,510 shows a device using a pair of mechanical straps with small protuberances holding a weight in position. Vibration of the device shakes the straps and the weight falls against a weight support member, spreading the straps against spring tension. The shock must be sufficient to release the upper protuberances from the keeper member 38. The end of the rod contacts a switch located in the bottom of the device. This device is complicated and requires careful balance. Again, since it is entirely mechanical, there is a danger of the parts hanging up.
U.S. Pat. No. 4,262,289 shows a pendulum operated alarm switch. No means is shown for cutting off a power supply. The metal straps holding the switch contacts might not close if the force is exerted along the edge of the straps rather than the face of the straps. The device includes gears and adjusting means which render it expensive to manufacture.
U.S. Pat. No. 3,858,131 shows a switch device for an alarm. It includes a resilient arm with switch contacts on it. Electromagnetic means is provided to maintain the resilient arm in the neutral position when movement of the arm is not desired. Dual contacts are required to operate the device with four contact points and the four contact arms. Two electromagnets are also required. Again, force acting at a right angle to the contact arms will not close the contacts as desired to actuate the alarm. No means is provided for shutting off a power source.
U.S. Pat. No. 2,912,535 discloses a complex temperature and earthquake responsive switch. A ball moves off its centered position when vibration occurs and the associated shaft is tilted as shown in FIG. 3 of the drawings. A spring urges the moveable contact member out of engagement from one contact and into engagement with the alarm contact. This device is complicated and involves mechanical unseating of the rod from the projection on the moveable contact element.
It is an object of the present invention to provide a new and improved device for interrupting electrical power when dangerous vibrations occur such as with an earthquake, which device is simple in construction and positive in operation without requiring springs, gears and other comparable items.
It is a further object of the present invention to provide such a new and improved device that is sensitive and does not depend upon mechanical operations for energizing the device.
It is another object of the present invention to provide such a new and improved device that is practical to build and that includes simple means for testing the device and for resetting it after it has been actuated.